Animal studies can contribute to addressing the issue of possible greater health risk for children exposed to 50-60 Hz extremely low frequency (ELF) magnetic fields (MFs), mostly in terms of teratological effects and cancer. Teratology has been extensively studied in animals exposed to ELF MFs but experiments have not established adverse developmental effects. Childhood leukaemia has been the only cancer consistently reported in epidemiological studies as associated with exposure to ELF MFs. This association has been the basis for the classification as "possibly carcinogenic to humans" by the International Agency for Research on Cancer in 2002. Animal experiments have provided only limited support for these epidemiological findings. However, none but one study used an animal model for acute lymphoblastic leukaemia (ALL), the main form of childhood leukaemia, and exposures to ELF MFs were not carried out over the whole pregnancy period, when the first hit of ALL is assumed to occur. Moreover, there are no generally accepted biophysical mechanisms that could explain carcinogenic effects of low-level MFs. The radical pair mechanism and related cryptochromes (CRY) molecules have recently been identified in birds and other non-mammalian species, as a sensor of the geomagnetic field, involved in navigation. The hypothesis has to be tested in mammalian models. CRY, which is part of the molecular circadian clock machinery, is a ubiquitous protein likely to be involved in cancer cell growth and DNA repair. In summary, we now have some clues to test for a better characterization of the interaction between ALL and ELF MFs exposure.
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